Almost every week during the fall and spring semesters the EEB has a departmental seminar in which a member of the faculty invites a researcher to give a presentation about their work. Typically the department seminar is held on Thursdays at 4pm in BPB 130. Often the seminar presenter will be available on campus for one or two days prior to their talk, in order to meet with interested students and faculty by appointment. EEB department seminars sometimes alternate with seminars in the Edwin Way Teale Lecture Series, which occur less frequently. One departmental seminar per year is organized by the graduate students, who invite the speaker and arrange his or her schedule. The department also holds the Monday Evening Seminar periodically throughout the semester. Schedules from previous semesters are archived here.

Spring 2008 Regular Seminars

07 January 2008

Mechanistic distribution models that link individual energetics and population dynamics enable investigating how morphology, physiology, and behavior influence species’ responses to environmental change. I discuss developing and field testing the models for Caribbean lizards along elevation gradients. I then apply the models to investigate the range implications of geographic trait variation among populations of North American lizards. The predicted extent of the northward range shift following climate warming depends on population traits. The research highlights the limitations of correlative range models and demonstrates the importance of considering adaptation, species’ interactions, and dispersal limitations when predicting ranges. Ongoing work aims to incorporate these biotic factors into mechanistic distribution models. I close by considering the broader context of energetic, ecological, and phylogenetic constraints on global patterns of reptile abundance and amphibian diversity in changing environments.

10 January 2008

Brian J. McGill

Patterns and processes in the variation of abundance between species and across space

Understanding the abundance and density of organisms (number of individuals per area) is a central question in ecology for both basic and applied reasons. Using the Breeding Bird Survey it is possible to partition variance across space, time, and taxon. The somewhat surprising results show that the largest component is actually variance within one species across space, a relatively unexplored pattern. Considerable variance also occurs between species, but about half of this variance is deeply conserved in the phylogeny. I will present a theory that explains local variation in abundance (also known as the species abundance distribution) using a stochastic spatial approach. I will then explore what is known about the mechanisms explaining the assumptions underlying this theory

14 January 2008

Shannon LaDeau

The ecological drivers and consequences of West Nile virus in North America

Emerging infectious diseases present a formidable challenge to the conservation of native species. However, identifying the impacts of an introduced pathogen and distinguishing it from other forces that influence population dynamics is complex. Here, twenty potential avian hosts are examined for West Nile virus (WNV) impact across their North American population ranges. Significant changes in population trajectories, including dramatic declines, are demonstrated for seven species from four families and are consistent with a priori predictions and pathogen dispersal. Spatial and temporal heterogeneity in West Nile virus impact suggest important interactions among pathogen amplification, human land use and climate. These findings illustrate the potential consequences of pathogen emergence for a diverse faunal assemblage across broad geographic scales and underscore the complexity of subsequent community response.

17 January 2008

Generalizable theories in community ecology require that insights derived from local communities can be scaled up to explain species interactions across larger spatial scales. Adaptation and gene flow can play an increasingly important role in shaping species interactions across distant communities. Here, I explore how evolution alters the dynamics of species interactions in metacommunities – sets of communities linked by dispersal – through theory and experiments. In simulated metacommunities, I show that dispersal-mediated evolutionary and ecological dynamics interact to alter expectations of community assembly and species richness. Next, I examine how adaptation and gene flow shape the survival of pond salamander populations in New England that face heterogeneous predation risks from size-selective predators. Under common garden conditions, prey differed in their susceptibility to predation and foraging rates depending on their population and region of origin. A demographic model of adaptive prey foraging in response to size-selective predators accurately predicted evolved responses in salamander foraging rates and variation in survival patterns. However, nearby populations had more similar foraging rates than expected by chance, suggesting that gene flow also affects prey survival. Results demonstrate that spatial heterogeneity in predation risk, local adaptation, and gene flow from nearby populations shape salamander predator-prey interactions. An evolutionary perspective on metacommunities offers multiple future research avenues that address how adaptation and gene flow govern community invasibility, assembly, and richness. My work on pond salamanders in New England offers an empirical foundation on which to test these ideas in the future.

21 January 2008

Broad-scale patterns of species diversity have captured the attention of biologists for over two hundred years. Historically examined as a latitudinal diversity gradient, the global pattern has generated a large number of hypotheses over the past several decades. Unfortunately, most of these potential explanatory variables co-vary strongly with latitude and with each other, making it difficult to distinguish among hypotheses. I present two tests of one hypothesis, species-energy theory, that seek to disentangle the variable of interest, resource availability, from latitude and other co-variates. I first show that the geographical pattern of species richness in birds varies between the summer and winter as predicted by a simple model that equates spatial and seasonal variation in resource availability. I next present an experimental test of species-energy theory using Panamanian Drosophila communities in artificial microcosms. Both studies confirm the importance of resource availability for structuring ecological communities and for contributing to broad-scale patterns such as the latitudinal diversity gradient and species-area relationships.